1. Technical Field
The present invention is generally related to dispensing devices and, more particularly, to a cartridge dispensing system that facilitates higher material feed pressures than those in the prior art. Specifically, the present invention uses a cartridge retainer having a containment bore that substantially matches the cartridge so that the walls forming the containment bore support the cartridge when high pressure is applied by a pneumatic piston that seals the end of the cartridge.
2. Background Information
Various types of liquids, pastes, lubricants, sealants, gasketing compounds, and potting compounds, as well as other materials are sold in standard cartridges that are used in cooperation with dispensing devices to allow the user to dispense the material from the cartridge. These cartridges are typically plastic and are substantially cylindrical in shape with a threaded outlet port on one end and an open end on the opposite end. These cartridges include 2.5, 6, 12, 20, and 32 ounce sizes; 300 and 500 ml sizes; as well as 1/10 gallon sizes. The cartridges typically include a plunger that seals the open end of the cartridge. In the past, a ram is placed in the open end of the cartridge against the plunger to form a seal within the bore of the cartridge to push the material toward the outlet port. The pressure from the ram pressurizes the contents of the cartridge causing the material to flow from the outlet port. An outlet fitting is typically threaded onto the cartridge at the outlet port to allow the material to be routed to the necessary location.
There are two standard methods for generating pressure within known cartridges. Each of these methods hold the cartridge statically while force is generated on the ram. Force is generated in the first method by using a compressed gas. The second method uses a drive rod that is mechanically moved by an actuator.
The major limitation in current cartridge and dispensing device design is that they cannot reliably generate material pressures within the cartridge of greater than approximately 100 pounds per square inch. This limitation often causes problems when a cartridge contains a material with a high viscosity. Examples of these materials are heavy bodied greases and paste adhesives. The problem with the low pressure is that the flow rate of the material from the cartridge is too low to be desired in the art. It is thus desired in the art to provide a cartridge dispensing system that allows higher viscosity materials to be dispensed at a greater flow rate by providing higher pressure within the cartridge.
Simply applying a higher pressure to the cartridges in past dispensing devices resulted in two problems. First, the cartridge plunger formed a relatively loose seal with the cartridge allowing the material to leak back out around the plunger and the ram. Second, the cartridge was held in the dispensing device with a relatively loose fit. A sufficiently high enough pressure would cause the sidewall of the cartridge to fail because of the loose fit.
Another problem with current dispensing systems is that there is a relatively large amount of time and effort required to change a cartridge. Cartridges are typically loaded into a containment bore from one end requiring a sealed end cap to be removed or the drive rod to be completely retracted from the cartridge. Another problem is that the outlet port fitting must be unthreaded from the old cartridge and threaded into the new cartridge. These steps result in downtime and can contribute to material spillage and air entrapment in the material. It is thus desired in the art to provide a dispensing device that allows cartridges to be changed in and out of the device relatively easily. Another problem with the prior art is that a partially-used cartridge may need to be refrigerated between uses. The art desires a dispensing mechanism that allows a partially-used cartridge to be readily removed and stored in a different location without unsealing the contents of the cartridge.